A print belt concerned by the present invention is of the type comprising a support-forming strip (e.g. made of polyester), and a polymerized resin adhering to one face of the strip and forming printing characters.
Such a belt is used in letterpress or flexographic printing: it is placed as a closed loop around two rollers and it is rotated by them. A strip of paper (or the equivalent) for printing is pressed against the ink-impregnated printing characters.
A known method of manufacturing such belts is of the type comprising: a spreading step during which the liquid resin is spread over a flat surface; a photopolymerizing step during which only that portion of the resin which is to correspond to the printing characters is subjected to exposure to light so as to be solidified; and a removing step during which the non-photopolymerized resin is removed from the surface on which it has been spread.
In such a method, the liquid resin is spread over a plane sheet, it is then exposed to ultraviolet (UV) light, with a film forming the negative of the characters for printing being placed in the immediate vicinity of the resin, between the light source and the sheet. By means of such exposure, only that portion of the resin which is not hidden by the negative film (the portion which is to form the printing characters) is photopolymerized (and solidified). Once photopolymerization has been achieved, the non-photopolymerized liquid resin is removed from the sheet and the sheet is stuck to the support-forming strip.
The problem with such a method is the relatively long time required to implement it.
A previously-proposed solution is to arrange the pages in the negative in such a manner as to be able to place a maximum number of pages in a negative film, thereby reducing the number of sheets used. Consequently, once the non-polymerized resin has been removed from the sheet, the sheet needs to be cut up so as to separate the pages from one another, and then the pages of characters need to be stuck to the support-forming strip in an arrangement suitable for printing the book. Nevertheless, that method presents as a main drawback the need for a large amount of time to cut up and arrange the pages.